In a new paper online in Current Biology, Higashi et. al demonstrate two novel mechanisms by which dividing cells maintain junction integrity with their neighbor cells. 

Epithelial tissues are sheets of cells that coat and protect the organs and cavities in our bodies, such as in the intestine, mammary gland, and skin. Consisting of cells that adhere to one another, these tissues form a barrier that separates the inside from the outside. Specialized protein structures, called adherens junctions and tight junctions, form between cells to help them adhere to one another (like Velcro) and form a regulated barrier that determines which solutes and ions can pass through.  Cell division occurs frequently in many epithelial tissues. During the last step of cell division called cytokinesis, when one cell is pinched into two by a belt-like contractile ring, the cell changes shape rapidly, which in turn challenges the integrity of cell-cell junctions.  It is essential for epithelial tissues to maintain cell adhesion and their barrier function despite the challenge to cell-cell junction integrity presented by cell division. 

The researchers, who used live microscopy of dividing epithelial tissues in Xenopus frog embryos,  showed:  First, adherens junctions (the Velcro-like junctions) at the contractile ring are stabilized and reinforced by recruitment of a protein called vinculin.  Second, at the end of cytokinesis, two new specialized junctional structures called tricellular tight junctions are formed at either end of the new cell interface. 

These findings have significant implications for understanding how cell-cell junctions are normally remodeled during cell division and possibly during other morphogenetic movements.  Additionally, the findings may provide insights into what goes wrong when barrier function is disrupted in diseases such inflammatory bowel disease or when cell-cell adhesion is disrupted during cancer cell metastasis. 

Maintenance of the Epithelial Barrier and Remodeling of Cell-Cell Junctions during Cytokinesis
Tomohito Higashi, Torey R. Arnold, Rachel E. Stephenson, Kayla M. Dinshaw, Ann L. Miller  
Current Biology (2016),